Condition monitoring is the process of determining the condition of machines comprising rotating components while the rotating components are in operation. Condition monitoring enables the repair of problem components prior to their failure and not only helps plant personnel reduce the possibility of catastrophic failure, but also allows them to order parts in advance, schedule manpower, and plan other repairs during downtime.
Rotating components such as bearings are often used in critical applications, wherein their failure in service would result in significant commercial loss to the end-user. It is therefore important to monitor such rotating components in order to plan intervention in a way that avoids failure in service, while minimizing the losses that may arise from taking the machinery in question out of service to replace the bearing.
The residual life of a rolling-element bearing is generally determined by fatigue of the operating surfaces as a result of repeated stresses in operational use. Fatigue failure of a rolling element bearing results from progressive flaking or pitting of the surfaces of the rolling elements and of the surfaces of the corresponding bearing races. The flaking and pitting may cause seizure of one or more of the rolling elements, which in turn may generate excessive heat, pressure and friction.
Bearings are selected for a specific application on the basis of a calculated or predicted residual life expectancy compatible with the expected type of service in the application in which they will be used. However, this type of life prediction is considered inadequate for the purpose of maintenance planning for several reasons.
One reason is that the actual operation conditions may be quite different from the nominal conditions. Another reason is that a bearing's residual life may be radically compromised by short-duration events or unplanned events, such as overloads, lubrication failures, installation errors, etc. Yet another reason is that, even if nominal operating conditions are accurately reproduced in service, the inherently random character of the fatigue process may give rise to large statistical variations in the actual residual life of substantially identical bearings.
In order to improve maintenance planning, it is common practice to monitor the values of physical quantities related to vibrations and temperature to which a component, such as a bearing, is subjected in operational use, so as to be able to detect the first signs of impending failure.
In a condition monitoring system data is usually obtained from at least one sensor provided on a machine housing close to the rotating component that is to be monitored and this data is usually transmitted in a wired or wireless manner and displayed to an analyst. This can however result in long transmission and display times and the data can be difficult to display or interpret. The transmission, display, storage and interpretation of such data can require a significant amount of energy, time and expertise, and consequently decreases the rate at which measurements and analyses can be made.